This invention relates to a dual point external load suspension implement adapted to be fitted to a rotary wing aircraft or the like enabling the aircraft to carry external loads with maximum flight stability.
Flights with loads externally suspended from a single suspension point oftentimes are restricted in their performance because of load instability. Helicopter flight stability may be enhanced by utilizing a two point suspension from the aircraft to the load. Conversion of a single hook aircraft can be accomplished by attaching a dual hook load beam to an existing single hook attachment point on the aircraft and by securing a beam in longitudinal direction to the aircraft by means of the single main cargo hook and by adding a second suspension point to the aircraft structure.
In applications requiring jettisoning of an external load, there exist problems of reliability in insuring that the coordinated release of each of the attachment points to the aircraft is effected. The two suspension points must provide positive support for the beam while providing a reliable release mechanism that is dependent only on the actuation of the main hook release system for the main aircraft cargo hook. The load must also be free to sway about an axis parallel to the longitudinal axis of the aircraft to prevent degradation of the aircraft performance in regard to roll motion.
A previous attempt to provide a passive release capability at one of the two suspension points utilized a ball and socket joint at the end of a "shepherd's crook". The ball and socket joint was the pivot point for sway motion, while the "shepherd's crook" locked the assembly as the beam was rotated to its locked horizontal position. When the primary suspension point was released, the beam rotated downwardly and rolled the "shepherd's crook" along a bearing until it was free to fall clear.
However, the "shepherd's crook" approach required complex and critical machining at both the "crook" bearing surface and the ball and socket joint. When applied to an existing single point suspension, this system had the further disadvantage of either requiring modification to the aircraft for internally mounting the ball and socket or having an external mount with a swing axis which was not coincident with that of the primary suspension hook, thus inducing out-of-plane loads which adversely affected the stability of the aircraft and which caused fatigue design problems.
Reference may be made to such U.S. Pat. Nos. 2,953,330 and 4,138,078 which disclose dual point suspension beams in the same general field as the present invention.